PROJECT SUMMARY The proposed R21 project will conduct two studies aimed at enhancing the effectiveness and scalability of the Mothers and Babies 1-on-1 Course (MB) among home visiting (HV) programs. MB is a manualized 12-session intervention guided by cognitive-behavioral therapy and attachment theory. Each session lasts 15-20 minutes and is delivered as part of a regularly scheduled home visit. Previous MB trials suggest that the intervention is less successful for women who exhibit smaller changes in hypothesized intervention mechanisms and less fully engage in completion of personal projects. To address this limitation, Study 1 will determine the feasibility and acceptability of conducting MB-TXT, in which HV clients receive MB supplemented by a series of weekly text messages focused on skill reinforcement, personal project reminders, and self-monitoring of depressive symptoms. We will also calculate a preliminary effect size that could be used to calculate sample size necessary for a future fully powered RCT that examines MB-TXT efficacy. We will conduct a cluster RCT in which we randomize 3 HV programs to implement MB and 3 programs to implement MB-TXT. We will recruit 108 study participants (54 MB, 54 MB-TXT) with mild to moderately severe depressive symptoms and conduct baseline, 6-month, and 9-month assessments to assess depressive symptoms and hypothesized intervention mechanisms. Feasibility and acceptability data will be collected from clients and home visitors to assess percentages of received text messages, home visitor adherence to sending texts at specified intervals, and clients' perceptions of text message utility and clarity. Previous postpartum depression preventive interventions?including MB?have neglected to intervene with partners of pregnant women despite growing recognition that paternal depression exerts influence on children's social-emotional development. To address this limitation, Study 2 will develop a MB-DAD intervention protocol that provides text messages to male partners of HV clients. Focus groups with Study 1 RCT participants, their male partners, and HV staff will be used to develop the MB-DAD curriculum and protocol. MB-DAD text messages aim to improve the mental health of the male partner and help him support his partner's mental health. We will examine the feasibility and acceptability of implementing the MB-DAD protocol and assess paternal and dyadic outcomes across two HV programs. We will recruit 24 mother-father dyads for an uncontrolled pilot in which mothers receive MB-TXT and fathers receive MB-DAD. Feasibility, acceptability, and outcome measures used in Phase 1 will be supplemented with assessments of fathers' mental health and partners' relationships. Participant assessments will be conducted at baseline and 6 months. The public health significance and innovation of this project is substantial. If we are able to integrate MB-TXT and MB-DAD into HV programs and generate improved mental health outcomes for HV clients and their partners, we will be prepared to replicate this intervention across HV programs nationally at a time when HV is rapidly proliferating through Affordable Care Act funding.